Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders.

---

[ Follow Ups ] [ Post Followup ] Thread: [ Display  All  Email ] [ Tube DIY Asylum ]

---

[ Alert Moderator ]

---

multimeter is reading very high plate current

Posted by banpuku (A) on February 20, 2017 at 11:44:50

I have been struggling with measuring the plate current on my ECC99 tube. I break the circuit and use my multimeter and get measurements well above 100mA. So, I put in different tubes (12BZ7) and adjusted the plate load resistor and cathode bias LED (I use LEDs instead of a resistor/cap) accordingly. The 12BZ7 tubes also measure very hot plate current, once again well above 100mA.

So, I am wondering about 2 things:

1. Is my multimeter measuring current correctly?

2. If the multimeter is OK, then how do I get the plate current significantly lower?

Schematic is attached.

thanks for any input.

***************************
UPDATE:

When measuring mA, I needed to put the multimeter lead into the AMP plug-in instead of the V/Ohm plug-in. My amateur mistake. that said, I got very nice feedback regarding voltage swing and will be upping the bias voltage to -4V.
Thanks to all who responded!

****************************

UPDATE #2 2/21/17

I think there is something wrong with my multimeter. After reviewing all of the plug-ins on the multimeter, there are actually 2 spots where "current" can be measured. 1) 10A and 2) 200mA. I was using the 200mA plug-in and was getting the bad readings. I think its time to get a fluke.

********************************

Pat

Edits: 02/20/17 02/21/17

This post is made possible by the generous support of people like you and our sponsors:

Schiit Audio

---

[ Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2024, Audio Asylum, all rights reserved ]

---

[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]

---